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AssigneeDow Global Technologies LLC
InventorsLi-Min Tau, Pak-Wing S. Chum, Seema Karande, Clive Bosnyak
Estimating the term…
Films with excellent machine direction (MD) tear properties comprise at least one layer made from a polymer comprising: (A) at least 50 weight percent (wt %) propylene; and (B) at least 5 wt % ethylene and/or one or more unsaturated comonomers. Representative of component (B) unsaturated comonomers are the C4-20 α-olefins, C4-20 dienes, styrenic compounds, and the like. Preferably, the film has at least one of a (i) haze value of less than about 10, (ii) 45 degree gloss of greater than about 65, and (iii) dart value of greater than about 100 g/mil. In one preferred embodiment, the layer comprises a compolymer characterized as having at least one of the following properties: (i) 13C NMR peaks corresponding to a regio-error at about 14.6 and about 15.7 ppm, the peaks of about equal intensity, (ii) a B-value greater than about 1.4 when the comonomer content, i.e., the units derived from ethylene and/or the unsaturated comonomer(s), of the copolymer is at least about 3 wt %, (iii) a skewness index, Six, greater than about −1.20, (iv) a DSC curve with a Tme that remains essentially the same and a Tmax that decreases as the amount of comonomer, i.e., the units derived from ethylene and/or the unsaturated comonomer(s), in the copolymer is increased, and (v) an X-ray diffraction pattern that reports more gamma-form crystals than a comparable copolymer prepared with a Ziegler-Natta (Z-N) catalyst.
A film comprising a first layer, the first layer having a machine direction tear of at least about 75 g/mil and comprising a first polymer, the first polymer comprising:
A film having a heat seal initiation temperature of less than about 110 C., and a minimum hot tack strength of 1 N/in at 100 C.
A film having at least one layer made from a polymer blend of at least two polymers comprising at least one polymer (A) comprising at least 50 weight percent of the blend and in which (A) comprises at least about 60 weight percent of units derived from propylene and at least about 4 weight percent of units derived from a comonomer selected from the group consisting of ethylene and an unsaturated monomer other than ethylene, and is characterized as having at least one of the following properties:
A blend comprising two or more polymer components in which a first component comprises at least about 60 weight percent of units derived from propylene and at least about 4 weight percent of units derived from a comonomer selected from the group consisting of ethylene and an unsaturated monomer, and is characterized as having at least one of the following properties:
A sealant composition comprising:
Dependencies are inferred from the claim text.
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Manufacture of articles or shaped materials containing macromolecular substances: manufacture of films or sheets
Layered products comprising a layer of synthetic resin: comprising polyolefins
Compounds containing elements of groups 4 or 14 of the periodic table
Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double
Term end not estimated
This invention relates to films comprising polypropylene. In one aspect, the invention relates to films comprising isotactic copolymers of propylene and at least one of ethylene and an unsaturated comonomer while in another aspect, the invention relates to films comprising polymer blends in which at least one blend component is a copolymer of propylene and at least one of ethylene and an unsaturated comonomer.
Polypropylene in its many and varied forms is a long established staple of the polymer industry. Depending upon its form, it exhibits a number of desirable properties including toughness (as measured by any of a number of impact tests, e.g., notched Izod, dart drop, etc.), stiffness (as measured by any of a number of modulus tests e.g., Young's), clarity, chemical resistance and heat resistance. Often a particular combination of properties is desired that requires a balancing of various properties against one another (e.g., stiffness against toughness).
Crystalline polypropylene, typically a homopolymer, is used extensively in various moldings because it exhibits desirable mechanical (e.g., rigidity) and chemical resistance properties. For applications that require impact resistance (e.g., automobile parts, appliance facia, packaging, etc.), a copolymer of propylene and ethylene and/or one or more α-olefins is used, or a blend of crystalline polypropylene with one or more polymers that exhibit good impact resistance, e.g., ethylene-propylene (EP) and/or ethylene-propylene-diene (EPDM) rubber. For applications that require toughness and/or heat resistance (e.g., films), preferably the polypropylene has a relatively low melt flow rate (MFR) or expressed alternatively, a relatively high weight average molecular weight (Mw). For applications that require good processing characteristics (e.g., fibers), preferably the polypropylene has a relatively narrow polydisperity or molecular weight distribution (MWD), e.g., less than 3.5.
FIG. 1 illustrates the unusual comonomer distribution of a propylene/ethylene (P/E*) copolymer made with a metal-centered, heteroaryl ligand catalyst.
FIGS. 2A and 2B show a comparison of the DSC heating traces of the propylene/ethylene (P/E) copolymer of Comparative Example 1 and the P/E* copolymer of Example 2, respectively.
FIG. 3 shows a comparison of the Tg data of a P/E* copolymer and a conventional Ziegler-Natta (Z-N) catalyzed P/E copolymer at equivalent crystallinity.
Molecular Weight
The weight average molecular weight (Mw) of the polymers used in this invention can vary widely, but typically it is between about 30,000 and 1,000,000 (with the understanding that the only limit on the minimum or the maximum Mw is that set by practical considerations). Preferably the minimun Mw is about 50,000, more preferably about 75,000 and even more preferably about 100,000. “High molecular weight”, “high weight average molecular weight”, “high Mw” and similar terms mean a weight average molecular weight of at least about 250,000, preferably of at least about 300,000 and more preferably 350,000, and more preferably at least about 400,000.
Polydispersity